Toddlers with a substantially greater amount of cerebrospinal fluid (CSF) at six and 12 months of age may be predicted with nearly 70 per cent accuracy to be at risk of developing autism spectrum disorder (ASD), researchers claim.

The findings revealed that the more CSF at six months, as measured through MRIs, the more severe the autism symptoms were at two years of age and this was also associated with poorer gross motor skills, such as head and limb control.

Although, CSF is not a perfect predictor of autism, it predicted that babies may later be diagnosed with autism, the researchers said.
"We can't yet say for certain that improper CSF flow causes autism. But extra-axial CSF is an early marker, a sign that CSF is not filtering and draining as it should. This is important because improper CSF flow may have downstream effects on the developing brain; it could play a role in the emergence of autism symptoms," said Joseph Piven, Professor at University of North Carolina at Chapel Hill, US.

"That there's an alteration in the distribution of CSF that we can see on MRIs as early as six months, is a major finding," Piven said. 

In the study, published in the journal Biological Psychiatry, the six-month olds who went on to develop autism had 18 per cent more CSF than six-month olds who did not develop autism. 

Infants who developed the most severe autism symptoms had an even greater amount of CSF -- 24 per cent greater at six months.

"We know that CSF is very important for brain health, and our data suggest that in this large subset of kids, the fluid is not flowing properly. We don't expect there's a single mechanism that explains the cause of the condition for every child. But we think improper CSF flow could be one important mechanism," said Mark Shen, postdoctoral student at University of North Carolina.